[Feature] Readline keybind support

[michaelBelsanti]

Description

Support for common readline keybinds like Ctrl-W to delete a word or Ctrl-U to delete a line. Many terminal apps support these keybinds by default and I'm very used to them, so I've found it a bit challenging to write quickly in Nanocoder.

Use Case

Make it easier for people familiar with these keybinds to edit message.

Additional Context

• I have searched existing issues to ensure this is not a duplicate
• This feature aligns with the project's goals (local-first AI assistance)

[will-lamerton]

This is a great idea - will triage to be done for the next release :)